This invention relates to an automotive vehicle axle for front and rear drive applications. Such axles are typically formed of extruded metal tubing. The opposite ends of the tubular axle are inserted within sockets formed, for example, on a conventional wheel support yoke or in a conventional carrier or housing through which engine power is transmitted to the axle.
Various attempts to reduce the weight of components of an automotive vehicle have included forming tubular axles with portions that are thinner in wall cross-section where lesser loads are imposed upon the axle and, conversely, with thickened cross-section wall portions where the anticipated loads are greater. In such types of axles, the beam strength of the axles may be insufficient to resist bending or flexing of the axle under extreme loads. Moreover, the axle may rotate or twist relative to the sockets that hold the ends of the axle when extreme torsional loads are applied. Hence, it would be desirable to maintain the light weight of a tubular axle while at the same time substantially increasing its bending or flexing resistance and, also, its resistance to twisting or rotating relative to its supporting sockets.
The methods for cold forming or extruding metal tubular axles and simultaneously forming thinner and thicker wall thicknesses at pre-selected locations within the tubular axle, are known. For example, U.S. Pat. No. 3,837,205 issued Sep. 24, 1974, for a “Process For Cold Forming A Metal Tube With An Inwardly Thickened End,” issued to Joseph A. Simon, discloses the method for forming, by an extrusion-type process, tubular axles having a greater wall thickness at an end while maintaining a thinner wall thickness along its length. Similarly, U.S. Pat. No. 3,886,649 issued Jun. 3, 1975, for a “Process For Cold Forming A Metal Tube With An Inwardly Thickened End,” issued to Joseph A. Simon, discloses a cold forming process for providing a uniform wall thickness tubular axle having an increased wall thickness at an end. Another U.S. Pat. No. 4,292,831 issued Oct. 6, 1981, for a “Process For Extruding A Metal Tube With Inwardly Thickened End Portions,” issued to Joseph A. Simon, discloses a method for cold forming, in an extrusion-like process, thickened end portions on an otherwise thin wall axle. Lastly, U.S. Pat. No. 5,320,580 issued Jun. 14, 1994, for a “Lightweight Drive Shaft,” issued to Joseph A. Simon, discloses a drive shaft for automotive vehicles having varying wall thicknesses with splined ends for connecting the shaft to supporting structures.
As is known, automotive vehicle axles are periodically subjected to extreme loads, as for example, due to random, sudden contacts between the vehicle wheels and extremely rough road surface areas, which could damage the axles. Such loads may cause the axles to twist or rotate relative to their connecting sockets or may cause some bending or flexing of the axle. In order to avoid or limit such axle damages, the axle walls had to be made with a thicker cross-section than necessary for normal loads. Such heavier or thicker walls result in heavier weight axles. Consequently, the invention herein is primarily concerned with providing a lighter-weight axle, which is accomplished by using thin, cross-sectional wall thicknesses where feasible for handling normal loads, while simultaneously rigidifying or stiffening the axle wall along its top dead center and bottom dead center to preclude bending or flexing under sudden extreme loads. This also interlocks the axle ends within their connecting sockets and resists twisting of an axle or rotation of an axle relative to its sockets.